Clinical Investigation will be conducted in the Ophthalmological unit of UBTH in two phases. In the first phase 21 relatively young healthy subjects aged less than 50 yrs will be recruited for this study after their informed consent. They will have no previous systemic or ocular diseases and have an intraocular pressure of 19mmHg or less and a visual acuity of 6/6. Base line investigations will include the systolic and diastolic blood pressure, horizontal pupillary diameter and applanation tonometry. The subjects will be divided into three groups of seven each (A1, A2 and A3).